Fix lint (#60472)
Summary:
This PR fixes the `mypy` failure introduced by [`numpy` 1.21.0](https://github.com/numpy/numpy/releases/tag/v1.21.0) (by pinning `numpy` to 1.20, at least for now) and the `quick-checks` failure introduced by https://github.com/pytorch/pytorch/issues/60405.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/60472
Test Plan: The Lint workflow in GitHub Actions.
Reviewed By: walterddr
Differential Revision: D29313009
Pulled By: driazati
fbshipit-source-id: 53fd0e0549c26be5fc5d3c502c5891c56c83a32c
